Can a breathalyser give an incorrect result?

Yes. A breathalyser can give an incorrect or misleading result if it is used incorrectly, is not properly calibrated or is affected by external factors.

Even a high-quality breathalyser has some measurement uncertainty.

What can affect the result?

Alcohol remaining in the mouth

If you have recently consumed alcohol, residual alcohol in your mouth may affect the measurement.

Before testing, wait at least as long as specified in the manual, often 15–20 minutes after your last alcohol intake.

Calibration

A breathalyser that has not been calibrated according to the manufacturer’s recommendations may give incorrect readings.

Temperature

Many breathalysers are designed for use within a particular temperature range.

If the unit is too cold or too hot, the result may be affected.

Incorrect sampling

If you do not blow for long enough or with the correct airflow, some devices may display error messages or give unreliable results.

Sensor condition

The sensor may change over time and be affected by use, storage and age.

What should I do if the breathalyser gives different results?

Check that you are following the manual’s instructions and using the device within the correct temperature range.

Also check when it was last calibrated.

If the results continue to vary significantly, the device may need to be checked or calibrated.

Can I drive if the breathalyser reads 0.00?

A result of 0.00 does not guarantee that you are fit to drive. The device may have a margin of error, and other factors, such as fatigue or residual effects after alcohol consumption, may impair driving ability.

If you are unsure whether you are sober and fit to drive, do not drive.